Transcript Aquifer Media - Utah State University

Determination of Aquifer Vulnerability using
DRASTIC model across conterminous United States
By
Karthik Kumarasamy
Final Presentation of GIS in Water Resources
Utah State University
Overview
• Concept of groundwater vulnerability
• DRASTIC Model
• Data Sources and Preparation
• Comparison with Nitrate concentration
• Conclusion
Concept of groundwater vulnerability
Purpose: Management Tool to protect groundwater resources
Definition: Probability that a specific contaminant will be detected at or above a
specified concentration in the subsurface at a specific location (EPA definition)
Some Vulnerability assessment models
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DRASTIC
AVI
GOD
SEEPAGE
Ordinal Logistic Regression, etc
DRASTIC Model
DRASTIC
Empirical model developed by National Water Well Association and EPA
Parameters considered in DRASTIC
– Depth to water table
– Net Recharge
– Aquifer media
– Soil media
– Topography (slope)
– Impact of vadose zone media
– (Aquifer hydraulic) Conductivity
Final DRASTIC Index = 5D + 4R + 3A + 2S + 1T + 5I + 3C
Study Area:
Conterminous United States
Depth to water table
Source: STATSGO Database
Methodology:
• Link the attribute table of Each State and component table to get the
(Maximum value for the range in depth to seasonally high water table)
• Append each state to get the final US map
• (These steps are common for all maps using STATSGO data)
• The field is known as wtdeph
Ratings of depth to water table
Net Recharge
• Net recharge or groundwater recharge is estimated using
Williams and Kissel's equation:
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PI = (P - 10.28)2/(P + 15.43) for hydrologic soil group A
PI = (P - 15.05)2/(P + 22.57) for hydrologic soil group B
PI = (P - 19.53)2/(P + 29.29) for hydrologic soil group C
PI = (P - 22.67)2/(P + 34.00) for hydrologic soil group D
PI = average of A and D for Hydrologic soil group A/D
PI = average of B and D for Hydrologic soil group B/D
PI = average of C and D for Hydrologic soil group C/D
where,
» PI = Percolation index
» P = Annual average precipitation
Ratings of Net Recharge
DATA Source:
– PRISM for precipitation data
– STATSGO for soil hydrologic group
Ratings of Net Recharge
Ratings for Aquifer Media
Source: Shallow aquifers of conterminous United
States (Groundwater atlas of US)
•Other Rocks: 3
•Carbonate-rock aquifers: 8
•Igneous and metamorphic rock aquifers: 3
•Sand stone and carbonate rock aquifers: 6
•Sandstone aquifers: 6
•Semiconsolidated sand aquifers: 4
•Unconsolidated sand and gravel aquifers: 8
Rating of Aquifer media
Rating for Soil Media
(Done based on the Soil Hydrologic group)
• Source: STATSGO database
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A: 8
B: 5
C: 4
D: 3
A/D: 6
B/D: 4
C/D: 4
Rating of Soil Media
Topography
Topography (slope):
STATSGO soil database
Methodology
(sloepl + slopeh) /2 * (comppct/100)
Ratings
Rating of Topography
Impact of vadose zone
• Data from Groundwater Atlas (shallowest principal aquifers
of the conterminous United States) to determine the Vadose
Zone ratings
• Assuming that the same geology will be present above the
water table as well
Rating for Impact of Vadose zone
• Other Rocks: 1
• Carbonate-rock aquifers: 6
• Igneous and metamorphic rock aquifers: 4
• Sand stone and carbonate rock aquifers: 6
• Sandstone aquifers: 6
• Semiconsolidated sand aquifers: 5
• Unconsolidated sand and gravel aquifers: 8
Rating for Impact of Vadose zone
Ranges for Hydraulic Conductivity (GPD/ ft2)
(Freeze and Cheery, 1979)
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Other Rocks: little or no permeability
Carbonate-rock aquifers: 10-2 – 101
Igneous and metamorphic rock aquifers: 10-7 – 103
Sand stone and carbonate rock aquifers: 10-3 – 101
Sandstone aquifers: 10-3 – 101
Semiconsolidated sand aquifers: 1-103
Unconsolidated sand and gravel aquifers: 102 - 106
Ratings for Hydraulic Conductivity
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Other Rocks:
Carbonate-rock aquifers: 1
Igneous and metamorphic rock aquifers: 1
Sand stone and carbonate rock aquifers: 1
Sandstone aquifers: 1
Semiconsolidated sand aquifers: 8
Unconsolidated sand and gravel aquifers: 10
Ratings of Hydraulic Conductivity
DRASTIC Index
Nitrate concentration Data
• Source: usgs (NAWQA program)
• Values are the median values of NO3
concentration
Distribution of Nitrate concentration across United States
Conclusion
• Areas shown vulnerable by the DRASTIC model
spatially coincide with nitrate concentration wells
with high concentration of Nitrate
• Even though there is subjectivity in the rating of
parameters results match well
Thank you!!!!
Any Questions